Plasticizers are incorporated into a resin (usually a plastic or elastomer) to increase the flexibility, workability, or distensibility of the resin. The largest use of plasticizers is in the production of “plasticized” or flexible polyvinyl chloride (PVC) products. Typical uses of plasticized PVC include films, sheets, tubing, coated fabrics, wire and cable insulation and jacketing, toys, flooring materials such as vinyl sheet flooring or vinyl floor tiles, adhesives, sealants, inks, and medical products such as blood bags and tubing, and the like.
Other polymer systems that use small amounts of plasticizers include polyvinyl butyral, acrylic polymers, nylon, polyolefins, polyurethanes, and certain fluoroplastics. Plasticizers can also be used with rubber (although often these materials fall under the definition of extenders for rubber rather than plasticizers). A listing of the major plasticizers and their compatibilities with different polymer systems is provided in “Plasticizers,” A. D. Godwin, in Applied Polymer Science 21st Century, edited by C. D. Craver and C. E. Carraher, Elsevier (2000); pp. 157-175.
Plasticizers can be characterized on the basis of their chemical structure. The most important chemical class of plasticizers is phthalic acid esters, which accounted for about 85% worldwide of PVC plasticizer usage in 2002. However, in the recent past there has been an effort to decrease the use of phthalate esters as plasticizers in PVC, particularly in end uses where the product contacts food, such as bottle cap liners and sealants, medical and food films, or for medical examination gloves, blood bags, and IV delivery systems, flexible tubing, or for toys, and the like. For these and most other uses of plasticized polymer systems, however, a successful substitute for phthalate esters has heretofore not materialized.
One such suggested substitute for phthalates are esters based on cyclohexanoic acid. In the late 1990's and early 2000's, various compositions based on cyclohexanoate, cyclohexanedioates, and cyclohexanepolyoate esters were said to be useful for a range of goods from semi-rigid to highly flexible materials. See, for instance, WO 99/32427, WO 2004/046078, WO 2003/029339, U.S. Application No. 2006/0247461, and U.S. Pat. No. 7,297,738.
Other suggested substitutes include esters based on benzoic acid (see, for instance, U.S. Pat. No. 6,740,254, and also co-pending, commonly-assigned, U.S. Provisional Patent Application No. 61/040,480, filed Mar. 28, 2008 and polyketones, such as described in U.S. Pat. No. 6,777,514; and also co-pending, commonly-assigned, U.S. Patent Publication No. 2008/0242895, filed Mar. 28, 2008. Epoxidized soybean oil, which has much longer alkyl groups (C16 to C18) has been tried as a plasticizer, but is generally used as part of a PVC stabilizer system to protect the PVC polymer from thermally induced decomposition. Co-pending and commonly-assigned U.S. Patent Publication No. 2010/0159177 discloses triglycerides with a total carbon number of the triester groups between 20 and 25, produced by esterification of glycerol with a combination of acids derived from the hydroformylation and subsequent oxidation of C3 to C9 olefins, having excellent compatibility with a wide variety of resins.
Matsuda et al., “Synthesis and Properties of Dialkyl Esters of Benzylsuccinic Acid”, Kogyo Kagaku Zasshi, vol. 58, pp. 60-62 (1955) disclose C1-C6, C8, C10 and lauryl esters of benzylsuccinic anhydride. The C4, C6 and C8 esters demonstrated good plasticizing properties for polyvinyl chloride. The starting benzylsuccinic anhydride material was formed by treating 10 parts toluene with 1 part maleic anhydride in an autoclave.
JP32-000043 (1957) “Plasticizers for Polyvinyl Resins”, to Matsuda discloses C1-C8 esters of aralkylsuccinic acids, such as benzylsuccinic acid, p-methylbenzylsuccinic acid or p-toluoylisopropylsuccinic acid. The esters are disclosed as useful for plasticizing polyvinyl resins.
Matsuda et al., “Properties of Dialkylesters of Benzyl- and Hexahydrobenzylsuccinic Acid as Plasticizers and Lubricant”, Kogyo Kagaku Zasshi, vol. 60, pp. 286-288 (1957) disclose properties of dialkylesters of benzyl- and hexahydrobenzylsuccinic acid as plasticizers and lubricants. In particular, 2-ethylhexyl and n-octyl esters of benzylsuccinic acid appeared to be more promising as plasticizers for polyvinyl chloride.
Vol'chenko et al., “Plasticizing a Chloroprene Latex L-7 Polymer to Increase Frost-Resistance of Latex Products”, Kauchuk i Resina; vol. 26(4), pp. 15-17 (1967) disclose didecyl benzylsuccinate as a plasticizer for chloroprene latex.
EP 13506 B to Renshaw discloses plasticizers for vinyl chloride polymers containing aromatic diesters, non-aromatic diesters and optionally hydrocarbons. The aromatic diesters can be C3-C6 alkyl benzyl succinates.
U.S. Pat. No. 1,848,155 to Boehmer discloses esters of secondary butyl alcohols, wherein the ester can be a secondary butyl ester of phenylsuccinic acid.
Thus what is needed is a method of making a general purpose non-phthalate plasticizer having and providing a plasticizer having suitable melting or chemical and thermal stability, pour point, glass transition, increased compatibility, good performance and low temperature properties.